1. Field of the Invention
This invention relates to a heat resisting alloy which not only retains a high oxidation resisting property at a high temperature but also excels in tensile strength at high temperature and toughness at a room temperature.
2. Description of the Prior Art
The number of equipments and parts to be employed at a high temperature exceeding 1,000.degree.C has increased as a result of the industrial progress and the technical advancement attained during recent years. There are ever-increasing demands for heat resisting materials that can be used for parts exposed to high temperatures and heavy loads such as rocket shells, atomic thermoengines, combustion chambers and jet pipes of jet engines, parts of gas turbines, high temperature and high pressure apparatuses used in chemical industries, high temperature valves, etc. To meet the requirements for such heat resisting materials, there have been conducted many technical researches and thus many kinds of heat resisting alloys have been used. However, it is generally believed that heat resisting steel is applicable to temperatures below 800.degree.C while the heat resisting alloy containing nickel (Ni) or cobalt (Co) as a basic component is applicable to temperatures below 1,000.degree.C. At temperatures higher than the above temperatures, they not only deteriorate in strength but also greatly deteriorate in oxidation resisting property and cannot be used for a long period of time. Although ceramics and super heat resistant alloys such as molybdenum (Mo), niobium (Nb) and tantalum (Ta) alloys can be used for a long time at temperatures higher than 1,000.degree.C, such super heat resistant alloys have a very poor oxidation resisting property, which either restrict the applicable ambient and operating conditions or require an antioxidation surface treatment. On the other hand, ceramics lack ductility and resistance to thermal shocks. Ceramics tend to break due to sudden changes in temperature. Such conventionally employed high temperature materials thus possess many shortcomings and require improvement.